//variabel defined
if(isset($_POST['btn-signup']))
{
    $uname = trim($_POST['txt_uname']);
    $umail = trim($_POST['txt_umail']);
    $ktpid = trim($_POST['txt_ktp']);
    $upass = trim($_POST['txt_upass']);
 .
 .
 .
 ...dst

 stmt = $DB_con->prepare("SELECT user_name, user_email, no_ktp FROM `users` WHERE user_name=:uname OR user_email=:umail OR no_ktp=:ktpid");
                 $stmt->execute(array(':uname'=>$uname, ':umail'=>$umail, ':ktpid'=>$ktpid));
                 $row=$stmt->fetch(PDO::FETCH_ASSOC);